In pumping with liquids of varying viscosity with reciprocating piston pumps, it was found that the higher the viscosity of a liquid, the more quickly that liquid could flow through a given opening. When the opening is the ball valve of a pump, and when highly viscous liquids are being pumped, internal liquid pressure increases or spikes after intake due to excess flow of liquid taken in. This is because the same size opening is used for high viscosity liquids as for low viscosity liquids, which do not create a pressure spike. This increase in internal liquid pressure requires more energy to compensate for the pressure fluctuation, and thus decreases overall efficiency.